Call transmitter



Jan. 5, 1943. c. A. LOVELL Em 2,307,521

CALL TRANSMITTER Filed July 22. 1941 2 Sheets-Sheet l WI W2v 3934 CALOVELL lNVE/ VTORS: RFJMLLINA Jan. 5, 1943. c. A. LOVELL ETAL 3 5 CALL TRANSMITTER Filed July 22, 1941" 2 Sheets-Shoot 2 CALOVELL /NVENTOR$-' Rf". MALL/NA A T TOR/V5 Y Patented Jan. 5, 1943 2,307,521 oALL TRANSMITTER Clarence A. Lovell, Maplewood, N. J and Rudolph F. Mallina, Hastings on Hudson, and Leonard Vieth, Jackson Heights, N. Y., assignors to Bell Telephone Laboratories,

Incorporated, New

York, N. Y., a corporation of New York Application July 22, 1941, Serial No. 403,480

3 Claims.

tablishing talking connections.

The object of the invention is to improve the construction and operation mitters.

According to the invention, an actuating mechanism is provided having means by which pivoted hammer-like members are normally held in striking relation to tuned piano gravity or springs through means actuated by the keys the operation of in predetermined combinations for causing vibration of the piano wires in the field of the for generating alternating current signals repelectromagnetic device resenting the digits of the operated keys. Means is provided in the actuating mechanism for damping the vibrations of the operated wires prior to the operation of each successive key while means is provided for adjusting the tension and thereby the tuning of the piano wires to the desired signaling frequencies.

Other novel features and advantages of the invention will appear from the following description and the claims appended thereto, reference being had to the accompanying drawings in which:

Fig. 1 is a side elevation view showing the hammers operating mechanism in normal position, a number of operating parts being shown partly in section;

Fig. 2 is a partial top view of Fig. 1;

Fig. 3 is a side elevation view of the hammers operating mechanism, one of the keys being shown partly operated;

Fig. 4 is a side elevation view similar to Fig. 3

but showing one of the keys in its full-operated position with the bars and hammers controlled by that key in position following by the operation of the common retaining pawl;

Fig. 5 is a rear view of Fig. 4; Fig. 6 is a side elevation view of the hammers operating mechanism modified; and

Fig. 7 is a rear view of Fig. 6 shown with the wires and let fall by their release of such call transalternating current generator and a number of piano wires removed.

As shown in the drawings, the call transmitter of the invention consists of a base H) to which is secured, as by welding, a pair of upright members provided for supporting a shaft H at both ends, and on this shaft is pivotally mounted a set of ten manually operable numbered key members of the type shown by keys Kl, K2, K6, K1, K8 arranged in two horizontal rows, each key having at its free end a pair of downwardly extending lug elements, such as Ll, L2, provided for imparting movement by pairs to a set of five U-shaped bars Bl, B2, B3, B4 and B5 in ten predetermined combinations representing the digits of the manually operable keys.

Bars Bl, B2, B3, B4 and B5, Figs. 1, 2, 3, 4 and 5, are bent at right angles at both ends thereof to form arms pivoted on the shaft l2. These bars are yieldably held in engaged relation with the under-side of projections L| and L2 of the keys by retractile springs |3 best seen in Figs. 1, 2, 3 and 4, while the keys Kl, K2, K3, etc. are themselves yieldably held in normal non-operated position as shown in Fig. 1 by retractile springs I4, similar ends of retractile springs 3 and 14 being hooked to a common bar l5 secured at one end to an oblong-shaped mounting l6, as by screws SC, and its other end to the base It] by a screw I 1.

The adjacently disposed arms a| a2, a3, a4 and a5 of bars Bl, B2, B3, B4 and B5, respectively, are provided with downwardly extending projections Pl, P2, P3, P4 and P5 best seen in Fig. 5, formed with arms yl, g2, g3, g4 and 1/5 provided for a purpose which will be hereinafter described in detail.

The base I0 is provided with two upright members |8 and I9 serving for supporting a shaft 20,

and on this shaft is pivotally mounted a set of hammer-like elements 2|, 22, 23, 24 and 25 best seen in Figs. 2 and 5 disposed in striking relation to piano wires wl, w2, w3, 204 and w5, respectively, of different sizes and tensions for vibration between the poles of an electro-magnetic device consisting of mounting IS, the coil 28 and a magnet 21 with the similar disposed ends of wires w|, 202, etc. clamped between the mountings l6 and the bar |5 while the other ends of wires w| 1122, etc. are wound similar tapered pins 26 fitted in similarly shaped holes in the opposite end of mounting It, thus providing means for adjusting the piano wires 2| 22, etc. to their proper tensions.

The hammer elements 2|, 22, etc. are normally in a manner which will be hereinafter described in detail. The plate It is provided with two up right members 29 and 3|] serving to support a shaft 3| used for pivotally mounting a bar B of substantially L-shaped cross section having its side SI disposed vertically in engageable relation with shoulder portions formed at the free ends of hammers 2|, 22, etc. for holding the latter in the raised position following a partial operation of the keys in their movements to full operated position, while the horizontal side S2 of bar B is disposed in engageable relation with the lugs LS of projections yl, g2, etc. to cause the pivotal movement of this bar against the tension of its retractile spring 32 for releasing the hammers corresponding to the bars BI, B2, etc. which may be operated by the depressed keys. Springs 33, 34, 35, 36 and 31 which are formed in the manner of a comb 38 and secured to the coil magnet 21 as by screws 39 and 40 are provided for holding the hammers 2|, 22, etc. a small distance above the vibrative wires wl, w2, etc. following the striking of these wires to permit their vibrations between the poles of magnet 21 and thereby generating alternating current signals in the coil 28 and the telephone line (not shown) connected thereto.

In the modification of the transmitter mechanism shown in Figs. 6 and 7, the ten manually operable key members as Kl, Kt, etc. pivoted on shaft |2 are yieldably held in the non-operated position by individual retractile springs 44 having one of their ends hooked to a metallic strip 45 secured to the wire mountings l6 by screws I], while the other ends of these springs are hooked to the downwardly extending lugs 41 of these keys. Each of the ten keys is provided with a downwardly extending projection 40 in turn formed with two lugs ill and 42 extending at right angles to the plane of its body portion, the lugs 42 of the keys engaging their respective vibrative wires wl, w2, etc. when the keys are in normal non-operated position to perform functions which will be hereinafter described in detail while the lugs 4| are provided for moving their respective hammers 2| which are pivoted.

on shaft 20 in spaced or raised position relative to the wires wl, w2, etc. as shown in Fig. 6.

In this modification a pawl-like member 43 pivoted on shaft 3| is provided for each of the ten hammers 2| so that only the hammer associated with the depressed key is released for striking its own vibrative wire wl, w2, etc., as the case may be. Springs 54 secured to the mounting 55 of coil 46 serve for holding their respective hammers a small distance from the vibrative elements to free them, thereby permitting their vibrations between the poles of electromagnet 55 following the fall of the hammers 2| over these wires.

In a typical example of operation of the call transmitter shown in Figs. 1,2, 3, 4 and 5, the operation of any one of the keys as key KB, for example, is effective as shown in Figs. 3 and 4 to operate the U-shaped bars El and B simultaneously in one of the combinations through the engagement of these bars with lugs LI and L2 formed with key 6. The movements of bars BI and B5 and therefore the lugs LS carried by these cars from the position shown in Fig. 1 to the position shown in Fig. 3 is effective to release the hammers 2| and which fall by gravity on the top edge of the vertically disposed side SI of the pivoted L-shaped bar B, while the lug portions LS2 also formed with these bars release their respectively associated vibrative elements M and 105 so as to permit their vibration upon the second release of the hammers 2| and 25 as effected by the pivotal movement of the the return operation of said keys to normal.

L-shaped bar B imparted by the simultaneous engagement of lugs LS of bars BI and B5 with the horizontally disposed side S2 of the pivoted bar B.

The striking of the vibrative elements ml and w5 by hammers 2| and 25 cause their vibration between the poles of the alternating current generator for transmitting a corresponding signal through the telephone line connected thereto representing the digit of the key depressed.

Upon the release of the operated key by the operator this key is returned to normal by the tension of its own retractile spring M which movement is followed by bars BI and B5 under the tension of their respective retractile springs l3 while the pivoted L-shaped bar B is returned from the position shown in Fig. 4 to the position shown in Fig. 1 by the tension of its retractile spring 32 and the call transmitter is now ready for a successive operation.

In an example of operation of the modification shown in Figs. 6 and 7, the hammers 2|, 22, etc. which are held in the raised position through their engagement with lugs 4 I, carried by each of these keys are released upon the partial operation of their respectively associated keys so as to fall on the vertically disposed sides of their respective pawls 43 wherein the continued operation of the depressed key is eifective to impart a pivotal movement to its respective pawl against the tension of its retractile spring to cause the second release of this hammer for striking its vibrative element wl, w2, etc. the operation of:

which between the poles of electromagnet 55 is effective to transmit a signal of a frequency representing the digit of the depressed key to the telephone line.

It is understood that minor changes may be made in the invention without departing from the scope of the appended claims.

What is claimed is:

l. A call transmitter, comprising a set of keys,

vibrative elements, a hammer for each of said elements, a retractile spring for each of said keys, means operated by said keys for engaging said hammers for holding them at a distance relative to said elements, a plurality of pawls for holding said hammers at saiddistance following a partial operation of said keys, means carried by the firstmentioned means for operating said pawls during the continued movement of said keys for releasing said hammers for striking said elements to cause them to vibrate, automatic operating means for moving said hammers independently of said keys following the striking of said elements for permitting the vibration of the latter,.and other means carried by the first-mentioned means for damping the operation of said elements upon 2. In a call transmitter, a set of tuned piano wires, a set of keymembers, spring means for yieldably holding said keys in normal unoperated position, a shaft for pivoting said key members,

a set of bars pivoted on said shaft and extending in operative relation with means carried by said key members for operation in predetermined combinations, spring means for yieldably holding said bars in said relation, a second shaft, a plurality of hammer members pivoted on said second shaft, means carried by each of said bars for holding said hammer members at a predetermined distance relative to said piano wires, means for holding said hammer members at said distance following a partial operation of said key members, and means carried by said bars for operating said holding means to cause the release of said hammer members in said combinations for striking a number of said piano wires to cause their vibration, and electromagnetic means for translating said vibrations into electric signals corresponding to the operations of said key members.

3. In a call transmitter, a base, a mounting secured to said base, a set of piano wires secured at both ends to said mounting, a shaft, a set of key members pivoted on said shaft, each of said members having a pair of projections at their free end, a plurality of U-shaped bars pivoted on said shaft and extending transversely of said key members in engageable relation with said projections to be actuated in pairs in a plurality of predetermined combinations upon the operation of said key members, a second shaft, a plurality of hammer members pivoted on said second shaft, means carried by said U-shaped bars for holding said hammer members in striking relation to said wires, a third shaft, means common to said hammer members pivoted on said third shaft for holding said hammers in said relation upon the partial operation of any one of said key members, means carried by each of said key members for actuating said common means to cause the release of two of said hammer members in said combinations for striking two of said wires to cause their vibrations, other means carried by said U-shaped bar for damping the operation of said wires following the release of the operated keys by the operator, and automatically operable means for returning said common means in engageable relation to said hammer members following the return of said operated keys to normal.

CLARENCE A. LOVELL.

RUDOLPH F. MALLINA.

LEONARD VIETH. 

